Virus-like particle (VLP) vaccines are genetically engineered complexes of multiple copies of protein antigens in a particulate virus-like structure. Viral proteins presented as VLPs or recombinant vaccine are immunogenic. Methods of creating VLPs are provided in U.S. Patent Application Publication Number 2006/02167702. See also U.S. Patent Application Publication Numbers 2006/0088909; 2010/0047277; 2010/0196419; 2010/0330190; 2011/0097358; 2012/0052082, and U.S. Pat. No. 7,763,450.
Influenza is one of the most important viral diseases in humans, with significant medical and economic burdens. Vaccination is an effective approach for prevention of influenza infection. Available seasonal influenza vaccines are trivalent inactivated (killed) virus vaccines (TIV) or live, attenuated, trivalent influenza virus vaccine (LAIV). These vaccines are targeted to primarily induce neutralizing antibodies directed against the viral envelope protein HA as well as the NA of strains homologous to the virus used for vaccination. However, influenza viruses undergo changes in their surface protein over time, called antigenic drift, allowing them to evade the host immune system and to reduce the effectiveness of immunity to prior infections. Such drifted strains can compromise vaccine-induced immunity due to antigenic mismatch with the vaccine strain, and the resulting seroprotection rates can vary according to the antigenic distance between the vaccine strain and the circulating strain. In addition, unexpected occurrence of shifted strains (resulting from the replacement of HA and less frequently NA subtypes with novel ones) may cause influenza pandemics. Major limitations of the current vaccines include the need to produce new vaccines every season, uncertainty in choice of the correct strains, long production times as well as the fact that the vaccines are produced by a slow process requiring embryonated eggs. Also, the current vaccines do not protect against future influenza pandemics. Improved vaccines are therefore needed, not only for seasonal influenza, but also for potential new influenza pandemic strains.
Because of these limitations of current vaccines, a universal vaccine that is based on relatively conserved protein domains would be a promising approach. A precondition is the accessibility to antibodies of these domains on infectious virus particles, intact infected cells, or both. The M2 protein of influenza A viruses is a tetrameric type III membrane protein, exhibiting pH-dependent proton transport activity. It is expressed at high density on the plasma membrane of infected cells, and its conserved extracelluar domain (M2e) is accessible to M2e-specific antibodies. However, because only a few copies of M2 are incorporated into the envelope of influenza viruses and the small M2e is shielded by the large surface HA and NA from efficient interaction with immune effector cells, M2e is poorly immunogenic although it is highly conserved. Studies have shown that, although M2e-specific antibodies were not able to prevent infection, they restricted subsequent virus replication and reduced illness and deaths. See Treanor et al., J Virol, 1990, 64(3):1375-7.
The bacterial flagellar antigen flagellin is the natural ligand of Toll-like receptor (TLR) 5. Also, it can be recognized by an intracellular receptor Ipaf. It can be used as an adjuvant when co-administered with antigen in a physically associated form or mixture. As a protein adjuvant, flagellin can be genetically modified to produce different vaccine formulations. It has known that, in most isolates of Salmonella, two genes encode flagellar antigens. FliC encodes the phase I flagellin FliC, and fljB encodes the phase II flagellin FljB. These genes are coordinately expressed by a phase-variation mechanism. Both FliC and FljB share conserved N- and C-termini which form the flagellar filament backbone, and contain motifs recognized by cell surface TLR5 and cytoplasmic Ipaf.
A membrane-anchored form of the Salmonella Typhimurium phase I flagellin (FliC) can be co-incorporated into influenza VLPs as an adjuvant molecule. See U.S. Patent Application Publication No. 2010/0330190 and Wang et al., J Virol, 2008, 82(23):11813-23. The variable central region of FliC has been found to be unnecessary for its TLR5 binding activity. See Smith et al., Nat Immunol, 2003, 4(12):1247-53. Huleatt et al. Vaccine 2008; 26(2):201-14 disclose a universal influenza vaccine candidate comprising a recombinant fusion protein linking influenza M2e to the phase II flagellin (FljB). WO/2009/079564 discloses virus-like particles and a membrane-anchored flagellin constructed having repeats of M2e. Wang et al., PLoS One., 2010, 5(11):e13972, disclose that intranasal immunization with influenza VLPs incorporating membrane-anchored flagellin induces strong heterosubtypic protection.
Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract illness in infants and children worldwide. RSV has 10 genes encoding 11 proteins. The RSV fusion (F) and attachment glycoprotein (G) contain neutralizing antibody epitopes and several T-cell epitopes. See Olson & Varga, Expert Rev Vaccines, 2008; 7:1239-55, Moore et al., J Virol 2009; 83:4185-94, and U.S. Patent Application Publication Number 2011/0097358.
References cited herein are not an admission of prior art.